3 grams of baking soda is a small amount that measures 0.106 oz (3 g) by weight and 0.225 tbsp (3.33 mL) by volume. It is about 2 times the size of a marble when poured into a loose pile.

In kitchen measures
0.676 teaspoons
0.676 tsp · 0.225 tbsp · 0.014 cups
about 2 times the size of a marble
Baking soda typically ranges 0.85–1 g/mL depending on how it's packed. A firmly packed scoop weighs more.